Share libraries: dl.dll not found
lazarus / 62-General

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Borneq · 2019-12-12 20:48

I test https://www.freepascal.org/docs-html/current/prog/progse56.html
where is
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i Function
dlopen(name: pchar;mode: longint):pointer;cdecl;external ’dl’;Function
dlsym(lib: pointer; name: pchar):pointer;cdecl;external ’dl’;Function
dlclose(lib: pointer):longint;cdecl;external ’dl’;And I can't find
this library in FPC distribution.
I found only c:\svn\fpc\rtl\unix\dl.pp

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marcov · 2019-12-12 20:51

That code and example is for Linux only. A portable substitute is
probably using unit dynlibs

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Borneq · 2019-12-12 21:09

Thanks, it works (except, it can't change literals in example)
- what do SafeLoadLibrary? I read it save FPU state.
- how share GetMem/FreeMem along dll's/so's ?
- is possible export classes and use it?

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marcov · 2019-12-12 21:12

Quote from: Borneq on December 12, 2019, 10:09:06 pmThanks, it works
(except, it can't change literals in example)
- what do SafeLoadLibrary? I read it save FPU state.
- how share GetMem/FreeMem along dll's/so's ?
- is possible export classes and use it?

SafeLoadLibrary, I don't know exactly, for the rest see
https://wiki.freepascal.org/packages

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PascalDragon · 2019-12-13 08:29

Quote from: Borneq on December 12, 2019, 10:09:06 pmThanks, it works
(except, it can't change literals in example)
What do you mean?

Quote from: Borneq on December 12, 2019, 10:09:06 pm- what do
SafeLoadLibrary? I read it save FPU state.
It stores the FPU and SSE state on x86 processors before loading the
library and restores it afterwards.

Quote from: Borneq on December 12, 2019, 10:09:06 pm- how share
GetMem/FreeMem along dll's/so's ?
If you simply pass a memory to a library, but the library does not
free it (or the other way round) then it will work without problems.
However if you have memory that is allocated in e.g. the program, but
freed in the library then you need to use a shared memory manager. You
can either have both parts use the C memory manager by using the cmem
unit or you can pass the program's memory manager to the library (by
using GetMemoryManager and SetMemoryManager). A common memory manager
is also required if you want to pass managed types like AnsiString or
dynamic arrays between the program and the library. Interfaces work
without a common memory manager however.

Quote from: Borneq on December 12, 2019, 10:09:06 pm- is possible
export classes and use it?
Short answer: no
Long answer: as long as you don't rely on the RTTI (which includes is
and as operators as well as exceptions) you can use them. To use them
in a safe way requires working dynamic packages support which is still
a Work In Progress.